Immunoelectron microscopy will be used to study the distribution of the cytoskeletal (contractile) proteins actin, myosin, and tubulin in photoreceptors from normal and dystrophic retinas. Some of the tissue samples will be chemically fixed in aldehydes. Other samples will undergo physical fixation using slam freezing of the tissue against a polished copper surface at liquid nitrogen temperature. The chemically and physically fixes tissues will then be embedded in Lowicryl K4M or in LR White prior to the labeling of tissue sections with antibodies. Additional tissue will be lightly fixed in aldehydes, perfused with sucrose, and quick frozen in liquid nitrogen prior to the collection and labeling of ultrathin frozen sections. With this multi-technique approach, the affects of chemical fixation, and of the embedding resins, upon cytoskeletal protein antigenicity and cellular ultrastructure will be assessed. Recent studies suggest that an actin mediated contractile mechanism regulates outer segment disc morphogenesis, and that myosin and microtubules play a role in outer segment development and maintenance. In this project, the distribution of actin, myosin, and tubulin will be studied in developing photoreceptors from normal mice, and from rds and rdle mice with early onset retinal degeneration. The results will demonstrate the cytoskeletal protein distribution during normal outer segment development, and also indicate whether a defect in this distribution can lead to the breakdown in outer segment disc morphogenesis observed in rds and rdle mice. The distribution of the cytoskeletal proteins will also be studied in photoreceptors from RCS rats with late onset retinal degeneration, and from donor eyes of patients with Retinitis Pigmentosa. Any variations from the normal distribution will be documented. This will help us to determine whether the generating outer segments undergo a disorganized breakdown, or if the degeneration follows a methodical sequence of events indicative of a "de-differentiation" of the visual cells.